(1) Field of the Invention
This invention relates to a method of constructing reinforced concrete bridges and it includes bridges constructed by the method.
The conventional method of constructing such bridges utilises arches serving as a lower framework support for building the bridge in reinforced concrete.
(2) Description of the Prior Art
Such arches constitute scaffolding which is generally supported on the banks, particularly on the abutments, and on the eventual piers, and also on pilework arranged between the eventual piers. This method of procedure presents many disadvantages, especially with bridges to be constructed over navigable waterways. In fact, the river structure to be built necessitates recourse to caissons, temporary pilework, etc., which constitute obstacles to traffic on the reach of the river and which may not satisfy the requirements with regard to tidal clearance and the waterlogged surface of the site. Even if the bridge is to be constructed over waterways which are not navigable, the construction of the supporting structure generally necessitates pilework which may be undesirable because of the attendant obstacle to the free circulation of the water. Lastly, and whatever the field of application, the use of arches as a supporting structure is a procedure which entails considerable delays and costs and which, even in special cases, it may be virtually impossible to achieve because of the nature of the terrain, the spans to be obtained, etc.
It is theoretically possible to imagine a method of construction entailing recourse to a provisional construction comprising braced pylons mounted on the piers of the bridge to be built and supporting a horizontal girder which supports, in its turn, a lower scaffolding. The lower scaffolding, attached to the horizontal girder, is intended to support framework by means of stays which pass through the superstructure of the bridge and, in particular, the deck.
Not only would such a method be difficult to carry out because of the considerable height of the pylons, but it would pose very complex problems related, in particular, to the difficulties of overcoming the deformation of the support framework during concreting. The use of stays passing through the superstructure also constitutes a disadvantage.